Controlled atmosphere incubator system with oxygen probe

ABSTRACT

An oxygen stream is supplied to an incubation hood for diffusion therein at a rate such that a concentrated oxygen layer forms in the hood lower interior at a zone about a patient&#39;&#39;s head; displacement gas such as air is admitted into the hood upper interior to diffuse into the concentrated oxygen layer for reducing the oxygen concentration at the zone about the patient&#39;&#39;s head, and to effect exhausting from the hood of downwardly displaced gas containing breath expelled carbon dioxide; and the oxygen supply is controlled in response to sensing of the oxygen concentration in the hood to maintain within a predetermined range the oxygen concentration at that zone.

Umted States Patent 1151 3,680,557 Doniguian 45 A g, 1, 1972 [54] CONTROLLED ATMOSPHERE 3,252,458 5/1966 Krasberg .i ..128/ 147 INCUBATOR SYSTEM WITH OXYGEN 3,380,369 4/1968 Allander ..128/1 B PROBE 2,232,156 2/1941 Abeles ..128/395 Inventor: Thaddeus M Doniguian, Laguna 2,389,293 11/1945 Blosser ..128/185 X Beach Cahf' Primary ExaminerRichard A. Gaudet 73 Assignee: I.M.I., Division of Becton, Dickinson AssismmExaminer-J- Mltchell and Company, Newport Beach Attorneywhite, Haefliger and Bachand Calif. [57] ABSTRACT [22] F1led: May 6, 1970 An oxygen stream 1s supplied to an incubation hood PP 35,026 for diffusion therein at a rate such that a concentrated oxygen layer forms in the hood lower interior at a 52 US. Cl ..128/185, 128/191 A Zone a patients head; displacement gas Such as 51 Int. 01. .Q ..A61m 16/02 air is admitted M0 the interim diffuse [58] Field of search 128/185 203 194 1 B 191 A into the concentrated oxygen layer for reducing the 128/191 66 6 R 142 oxygen concentration at the zone about the patients 142 4 1425 2, M R head, and to effect exhausting from the hood of 5 downwardly displaced gas containing breath expelled carbon dioxide; and the oxygen supply is controlled in response to sensing of the oxygen concentration in the [56] References Cited hood to maintain within a predetermined range the UNITED STATES PATENTS oxygen concentration at that zone.

3,552,391 l/1971 7 Claims, 5 Drawing Figures Deaton ..l28/ 194 CONTROLLED ATMOSPHERE INCUBATOR SYSTEM WITH OXYGEN PROBE BACKGROUND OF THE INVENTION This invention relates generally to the control of atmosphere in an enclosure, and more particularly concerns apparatus and method for achieving this objective through taking advantage of the densities and diffusion properties of various gasses such as air, oxygen,

' nitrogen, and carbon dioxide present in the atmosphere SUMMARY OF THE INVENTION It is a major object of the invention to provide an incubation system and method characterized as satisfying the above needs and requirements, affording unusually advantageous results. Basically, the method involves the steps of supplying oxygen in a gaseous stream into an incubation hood for diffusion therein at a rate characterized in that a concentrated oxygen layer forms in the hood lower interior and at a zone about a patients head; admitting displacement gas (as for example air) into the hood upper interior to diffuse into the concentrated oxygen layer at the top thereof for reducing the oxygen concentration at the zone, and exhausting to the exterior of the hood the downwardly displaced gas in the layer containing breath expelled carbon dioxide; and sensing the oxygen concentration of the gas in the layer and controlling the oxygen supply to maintain within a predetermined range the oxygen concentration at the head zone. As will appear, the oxygen supply is typically carried out to diffuse the supply stream in a laminar flow path circulating about the lower interior of the hood, thereby to produce the layer as described facilitating accurate oxygen concentration control at the head zone.

In its apparatus aspects, the equipment comprises the hood having upright wall means for receiving a patients head in a hood lower interior zone; means to supply oxygen in a gaseous stream into the hood for diffusion therein to form the layer, the hood upper and lower interiors each having such communication with the exterior that displacement gas may enter the hood upper interior to diffuse into the top of the layer'for reducing the oxygen concentration at the head zone, and also for downwardly displacing gas in the layer containing breath-expelled carbon dioxide; and control means to sense the oxygen concentration of gas in the layer and to control the oxygen supply thereby to maintain the oxygen concentration at the patients head within a predetermined range. As will be seen, the control means typically includes an oxygen concentration sensor mounted to project in the hood at the level of the layer to which oxygen is supplied by diffusion under laminar flow conditions so as not to disturb the concentration measurement and maintenance. Also, the control means may typically include a valve controlling the oxygen supplying gas stream and an operator responsive to the sensor output to control valve operation to increase and decrease the stream flow in response to decrease and increase respectively in the oxygen concentration at the zone.

Additional objects and advantages of the invention include the provision of a laminar flow diffuser at the hood, the latter typically consisting of plastic sheet material; the provision of a flexible hood sheet with fastener joined end portions for disposability; the provision of through openings proximate the top and bottom of the hood to enable displacement gas and exhaust gas flow as described; and the provision of a heater disposed to radiate heat downwardly through the open top of the hood.

These and other objects and advantages of the invention, as well as the details of an illustrative embodi merit, will be more fully understood from the following description and drawings, wherein;

DRAWING DESCRIPTION FIG. 1 is an elevation, taken in section, showing a system incorporating the invention;

FIG. 2 is a perspective showing of an enclosure or hood as used in FIG. 1;

FIGS. 3 and 5 are elevations illustrating modified hoods, prior to assembly thereof; and

FIG. 4 is a perspective showing of the FIG. 3 hood after assembly.

DETAILED DESCRIPTION In the drawings, a hood is indicated at 10 as having upright generally curvilinear wall means 11 forming an enclosure for receiving an infants head 12 in a lower interior zone 13. The hood may advantageously comprise transparent plastic material which is transparent for use of viewing the infants head. The hood is also shown as having a transparent top 14 integral with the generally annular wall 11, and containing one or more openings 15. A side opening 16 in wall 11 is large enough to loosely receive the infants neck when the hood is placed downwardly as shown, the torso 17 projecting at the exterior. Thus, aperture means is provided to allow the patientshead to extend into the hood lower interior. A radiant heater 18 is shown projecting above the hood and supported on a pedestal l9, radiant heat passing downwardly through the openings 15 for warming the infants head and body.

Means is provided to supply oxygen in a gaseous stream into the hood and characterized in that a coricentrated oxygen layer forms in the hood lower interior. That layer may for example extend below the level indicated by broken line 20, and the oxygen supply means may include the source 21 of about percent oxygen; a valve 22 controlled by actuator 23; a flow meter 24; a manually controlled valve 25; a diffuser nozzle 26 and a flexible line 27 connecting the outlet of valve 25 with nozzle 26. The diffuser 26 is shown to have porting 28 located to direct the oxygen stream flow in paths indicated by arrows 29 circulating generally transversely (for example generally tangentially relative to the hood wall) under laminar flow conditions in the hood lower interior, so as to produce the layer referred to. In this regard, turbulent flow condi tions are to be avoided since a condition of instability will then result leading to loss of accurate control of the oxygen concentration at the patients head zone.

Regarding the desired stabilized condition of the oxygen rich layer, it will be noted that displacement gas, as for example air, enters the hood upper interior 30 as via top opening or openings 15, to diffuse into the oxygen layer at the top of the latter indicated between levels 20 and 31, for reducing somewhat the oxygen concentration at the top of zone 13. Thus, the upper surface of the approximately 100 percent oxygen will begin diffusing upwardly into the oxygen-nitrogen mixture above level 20, and the nitrogen in the air in zone 30 will diffuse downwardly into zone 13 above level 20. An intermediate layer thus forms in zone 13 and consisting of mixed oxygen and nitrogen varying in concentration between 21 and 100 percent oxygen between levels 31 and 20.

Also provided is control means to sense the oxygen concentration of gas in the layer between levels 20 and 31 and to control the oxygen supply to the space below level 20 thereby to maintain the desired oxygen concentration in the zone 13, and particularly at the level of the patients nose, i.e., within a predetermined range. As illustrated, such means may typically include the oxygen sensor 32, as for example of the type described in US. Pat. No. 2,913,386 to Clark; and the electrical connection between the sensor output and the valve operator 23. That connection may include a lead 33 and an oxygen controller 34, the operation being such that oxygen flow from source 21 is increased and decreased in response to decrease and increase respectively in the oxygen concentration at the level of the sensor between levels 20 and 31. Controller 34 may include a comparator having one input from the sensor and another input from a potentiometer controlled by a manually settable control 37. An error signal from the comparator and of sufficient magnitude operates the operator 23. Oxygen concentration is displayed at 34a.

The system operation is described as follows. Initially the hood will have an even distribution of air (approximately 21 percent oxygen and 79 percent nitrogen) throughout its interior as air will freely circulate through the appropriately sized holes in the top' 14 and exhaust parts 35 at the bottom of the wall 11. The oxygen sensor will sense the presence of 2] percent oxygen and transmit this information to the controlled 34 where the information is compared with the oxygen concentration desired according to an adjustable setting 37 on the controller. If the oxygen concentration sensed by the oxygen sensor is less than the desired setting on the controller, the latter will activate the operator 23 causing oxygen to flow from the oxygen source 21 through the flow indicator 24, the flow valve 25, the connecting hose 27, the diffuser nozzle 26 and into the enclosure. The flow valve is adjusted manually such that oxygen enters the 25 is to insure laminar movement of gasses therein. The difiuser nozzle causes oxygen entering the enclosure to diffuse in a generally circular path and form a layer of virtually 100 percent oxygen at the bottom of the enclosure. The upper surface of the 100 percent oxygen will begin diffusing up into the oxygen/nitrogen air mixture just above and the'nitrogen will begin diffusing down into the upper layers of the percent oxygen blanket, thus forming the above described intermediate layer of mixed oxygen and nitrogen varying in concentration between 21 to 100 percent oxygen.

If we assume that the desired oxygen setting at 37 on the oxygen monitor 34 is 40 percent, then 100 percent oxygen will continue to enter the bottom of the enclosure through the diffuser nozzle until the 40 percent oxygen/nitrogen mixture point within the diffusion layer above the 100 percent oxygen layer reaches the elevation of the oxygen sensor, at which time the operator will turn off valve 22 and oxygen will cease to enter the lower interior of the enclosure.

The 100 percent oxygen (1.43 g/l) being heavier than air 1.29 g/l) will tend to stay at the bottom of the enclosure and will slowly exit out the holes 35 in the bottom of the enclosure as long as all flow into the chamber is circumferentially laminar and no turbulence occurs. As the 100 percent oxygen flows out of the holes 35, the oxygen concentration at the sensor 32 will decrease until the concentration becomes less than 40 percent at which time the valve 22 will be opened allowing 100 percent oxygen to again enter the enclosure. The entire cycle will continue to be repeated, thus maintaining the concentration of oxygen at the tip of the sensor 32 to about 40 percent or to whatever concentration is set at the controller. Any object (such as the patients nose) within the enclosure at the same height as the tip of the sensor will experience the oxygen concentration as determined by the controller. Any carbon dioxide (1.98 g/l) generated within the enclosure by, for instance, the patients breath, will tend to diffuse downward and out through the holes 35 at the bottom of the enclosure, since carbon dioxide is heavier than either 100 percent oxygen or air.

The size of the openings 15 at the top of the enclosure that permit the entrance of air is not particularly critical. The openings act only to insure a laminar situation within the enclosure and if the enclosure is small enough and tall enough, the top may be left open completely. v

The size of the openings 35 at the bottom of the enclosure are more important, however, as they determine the rate of exit of the 100 percent oxygen at the bottom of the enclosure. Large holes will result in an unnucessary waste of oxygen and too small a hole will result in an undesired build-up of 100 percent oxygen.

The system described above is essentially an onoff system, whereby the electric valve is either on or off. If a suitable proportioning valve and controller are used instead of the on-off electric valve and controller, the 100 percent oxygen would enter the enclosure continuously at a rate determined by the controller and achieve essentially the same control ex cept possibly for greater accuracy.

The source of the oxygen as described above is shown as a wall outlet as is common in most hospitals. The source could also be pressure cylinders. Pre-mixed gasses or equipment such as proportioning nebulizers which dilute the source gas as well as humidify it could also be used. The block 48 indicates humidifying or nebulizing equipment connected at 49 with line 27, so that the patient does not experience dry oxygen. Such equipment may incorporate a heater, so that the oxygen supply is both moist and warm.

If desired, valve 22 and actuator 23 may be placed at the outlet side of manual control valve 25. Also, a certain amount of total oxygen may be supplied to valve 25 at 210, i.e., so as not to be controlled by valve 22. The latter is then used to control make-up oxygen supply as is necessary for control as described above. In situations where sterility is important, the enclosure could be designed utilizing inexpensive materials and in such a manner that the entire enclosure would be disposable after each use, thus circumventing the need for sterilization between each use. FIGS. 3 and 4 describe such a design. The enclosure 40 would be fabricated in a flat sheet fonn (as seen in FIG. 3) out of inexpensive plastic materials. Inexpensive snap fasteners 41 and 41a are incorporated at opposite longitudinal ends of the enclosure such that the enclosure can be assembled easily as seen in FIG. 4. Holes 42 are provided in the bottom of the enclosure for allowing the controlled gasses to escape. A hole 43 would also be provided for the oxygen line 44, and a larger hole 45 is formed to receive the infant patients neck. The enclosure top is entirely open as seen at 46.

The hood of FIG. 5 is like that of FIG. 3, excepting that the fasteners comprise hooks 50 at one end of the sheet 51, and eyes 52 at the opposite end of the sheet to receive the hooks.

Controller 34 may incorporate suitable temperature compensation such as a temperature sensitive resistance (i.e.,, thermistor) used with the sensor 32 so that the temperature of the resistance is the same as that of the gas adjacent the sensor. Such compensation eliminates the effect of temperature change upon the current flow from the sensor to the controller.

I claim:

1. In incubation apparatus, the combination compris-' a. a hood having upright generally curvilinear wall means with aperture means to allow a patients head to extend into a hood lower interior zone,

. means including an oxygen inlet port to disperse oxygen in a gaseous stream into the hood and generally tangentially of said wall means for diffusion therein and characterized in that a concentrated oxygen layer forms in the hood lower interior and at said zone, the hood having upper and lower through opening means the upper opening means located near the hood top to pass atmospheric air entering the hood upper interior to diffuse into said layer at the top thereof, for reduc ing the oxygen concentration at said zone, and also for downwardly displacing gas in said layer containing breath expelled carbon dioxide for discharge to the hood exterior, the lower opening means located near the bottom of the hood wall to pass to the exterior gas including oxygen displaced in said layer, and

c. control meansto sense the oxygen concentration of gas in said layer and to control said oxygen supply thereby to maintain the oxygen concentration at said zone within a predetermined range, said control means including an oxygen sensor effectively located between the levels of the oxygen inlet port and the top of the hood.

2. The combination of claim I wherein said control means also includes a valve operable to control said oxy en su lin aseous stream and an o erator re sponsiy t o tl e gutput of said sehsor to contr l valve operation to increase and decrease the flow of said stream in response to decrease and increase respectively in the oxygen concentration at said zone.

3. The combination of claim 2 wherein said means to supply oxygen in said stream includes a flow diffuser at said hood and having porting located to direct the stream flow in paths circulating generally transversely under laminar flow conditions in the lower interior of the hood, thereby to produce said layer.

4. The combination of claim 1 wherein said hood comprises transparent plastic sheet material.

5. The combination of claim 4 wherein said sheet is flexible and has joined opposite end portions.

6. The combination of claim 1 including a radiant heater disposed to radiate heat downwardly through the opening proximate the top of the hood.

7. In incubation apparatus, the combination comprismg a. a hood having upright generally curvilinear wall means with aperture means to allow a patients head to extend into a hood lower interior zone,

. means including an oxygen inlet port to disperse oxygen in a gaseous stream into the hood and generally tangentially of said wall means for diffusion therein and characterized in that a concentrated oxygen layer forms in the hood lower interior and at said zone, the hood upper and lower interiors each having such communication with the exterior via upper and lower through opening means respectively that displacement gas may enter the hood upper interior to diffuse into said layer at the top thereof, for reducing the oxygen concentration at said zone, and also for downwardly displacing gas in said layer containing breath expelled carbon dioxide for discharge to the hood exterior,

c. control means to sense the oxygen concentration of gas in said layer and to control said oxygen supply thereby to maintain the oxygen concentration at said zone within a predetermined range, said control means including an oxygen sensor effectively located between the levels of the oxygen inlet port and the top of the hood, and

d. a radiant heater overlying the hood to radiate heat downwardly into the hood interior. 

1. In incubation apparatus, the combination comprising a. a hood having upright generally curvilinear wall means with aperture means to allow a patient''s head to extend into a hood lower interior zone, b. means including an oxygen inlet port to disperse oxygen in a gaseous stream into the hood and generally tangentially of said wall means for diffusion therein and characterized in that a concentrated oxygen layer forms in the hood lower interior and at said zone, the hood having upper and lower through opening means the upper opening means located near the hood top to pass atmospheric air entering the hood upper interior to diffuse into said layer at the top thereof, for reducing the oxygen concentration at said zone, and also for downwardly displacing gas in said layer containing breath expelled carbon dioxide for discharge to the hood exterior, the lower opening means located near the bottom of the hood wall to pass to the exterior gas including oxygen displaced in said layer, and c. control means to sense the oxygen concentration of gas in said layer and to control said oxygen supply thereby to maintain the oxygen concentration at said zone within a predetermined range, said control means including an oxygen sensor effectively located between the levels of the oxygen inlet port and the top of the hood.
 2. The combination of claim 1 wherein said control means also includes a valve operable to control said oxygen supplying gaseous stream, and an operator responsive to the output of said sensor to control valve operation to increase and decrease the flow of said stream in response to decrease and increase respectively in the oxygen concentration at said zone.
 3. The combination of claim 2 wherein said means to supply oxygen in said stream includes a flow diffuser at said hood and having porting located to direct the stream flow in paths circulating generally transversely under laminar flow conditions in the lower interior of the hood, thereby to produce said layer.
 4. The combination of claim 1 wherein said hood comprises transparent plastic sheet material.
 5. The combination of claim 4 wherein said sheet is flexible and has joined opposite end portions.
 6. The combination of claim 1 including a radiant heater disposed to radiate heat downwardly through the opening proximate the top of the hood.
 7. In incubation apparatus, the combination comprising a. a hood having upright generally curvilinear wall means with aperture means to allow a patient''s head to extend into a hood lower interior zone, b. means including an oxygen inlet port to disperse oxygen in a gaseous stream into the hood and generally tangentially of said wall means for diffusion therein and characterized in that a concentrated oxygen layer forms in the hood lower interior and at said zone, the hood upper and lower interiors each having such communication with the exterior via upper and lower through opening means respectively that displacement gas may enter the hood upper interior to diffuse into said layer at the top thereof, for reducing the oxygen concentration at said zone, and also for downwardly displacing gas in said layer containing breath expelled carbon dioxide for discharge to the hood exterior, c. control means to sense the oxygen concentration of gas in said layer and to control said oxygen supply thereby to maintain the oxygen concentration at said zone within a predetermined range, said control means including an oXygen sensor effectively located between the levels of the oxygen inlet port and the top of the hood, and d. a radiant heater overlying the hood to radiate heat downwardly into the hood interior. 